Separate Outdoor reset control for second floor baseboard loop?

semma

Hello,
I just installed a Viega basic heating control made by tekmar for my basement/first floor radiant system. I've got a main loop for the basement slab and the first floor which supplies three stadler manifolds. This is all working fine. But, I've got a separate loop and circulator coming off the boiler for the second floor which is baseboard heat with one three zone manifold, three stats, and a zone controller with actuators on the second floor. The zone controller has an end switch that signals a relay in the basement to fire the circulator. Here's my question. Since this appears to be a different loop, is there anything to be gained by adding another outdoor reset, with outdoor sensor and supply temp sensor like a taco sr501-or ? The main loop for the first floor enables the boiler, has its own mixing valve, etc but the second floor appears to just call hot water when it needs it. Thanks!
Sal

bmwpowere36m3

Is the second floor not holding temp steady? Sounds like, the second floor only enables its circulator. The first floor or basement has to call for the boiler to actually fire.

Only benefit to another ODR curve is if the BB upstairs needs to run at a different temp. I assume, because the radiant zones are being "mixed" then the boiler doesn't get fired too often (is the boiler temps set high for the BB loop)? So the second floor could be calling for heat, but the boiler doesn't fire.

Can't you just wire the relay for the second floor to the boiler's aquastat. So when either "zones" call for heat the boiler will fire if its temps fall below setting.

semma

Bmwpower, thanks for your reply. The heat seems very reliable without a big differential on the second floor. You bring up a very good point. Isn't it true that the baseboard heaters require hotter supply temperatures? Perhaps this is why it is wired separately. I believe it is hooked directly to the aqua stat on the boiler. As you said, my boiler doesn't fire as often as it used to ever since I added the outdoor reset for the first floor. It's probably best to just leave it alone. There's probably not a huge savings in fuel and comfort doesn't seem to be an issue.

bmwpowere36m3

You can run lower temps with BB, to a point, if you install enough of it.

Dave H_2

Absolutely! If your zone heats fine on the coldest day of the year with 180F, then resetting the water temperature when it is not as cold can be done. The FuelMizer would be the easiest way to get that to happen.

bmwpowere36m3

You'd need to post more info on your boiler, setup and pictures would help... since it hard to know exactly how the boiler is setup. I'm guessing its setup for BB (so high supply temps) and the radiant zones are simply mixed down.

semma

Thanks, I wish I had your knowledge! I'm still a novice but a quick study I think. I will post some pictures tomorrow. It's a circa 1994 veissmann oil fired boiler. It's got a hot water system underneath. It's got a viessman control on the top which I believe is for the hot water limit. The veissmann control has a summer mode switch on it and some dials, one which is max water temp. There's a main supply pipe which splits into two branches. One branch goes to the radiant loop for the basement slab and the first floor gypcrete radiant. This loop has a stadler mixing station, Viega outdoor reset, indoor/outdoor sensors, diverter valve and actuator and a circulator. The outdoor reset that I installed all seems to work fine but we haven't had any sub-zero weather yet this year. This radiant loop serves three stadler manifolds, two on the first floor and one p in the basement. All together about 14 zones , valve actuators, and thermostats. The other branch off the boiler supply has a taco circulator on the supply side and it loops back to the boiler. This runs to a three zone stadler manifold on the second floor which is actuated by three room stats. It's all baseboard heat built almost flush to the wall. Ive never seen anything like it before. No visible fins like standard baseboard. I've also got a separate hot water on demand loop and its own circulator. I bought the house from my best college buddy who was in the oil business, made it big, and moved to Vegas. I think the design was quite modern for 1992 and I'm looking to tweak the best performance out of it with updated controls. It's a big house, 4400 sf, and the four 330 gallon oil tanks in the basement scare me a bit. So far, a very mild winter and we have only used about a tank of oil. The efficiency ratings over the years are in the high 80s like 87.5 and I think it's due mostly to low flue temps in the 300s. I'm posting some pictures but will get the boiler pictures tomorrow.